From: Trond Myklebust <trondmy@hammerspace.com>
To: "bcodding@redhat.com" <bcodding@redhat.com>,
"chuck.lever@oracle.com" <chuck.lever@oracle.com>
Cc: "tibbs@math.uh.edu" <tibbs@math.uh.edu>,
"bfields@fieldses.org" <bfields@fieldses.org>,
"linux@stwm.de" <linux@stwm.de>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"km@cm4all.com" <km@cm4all.com>
Subject: Re: Regression in 5.1.20: Reading long directory fails
Date: Sun, 8 Sep 2019 15:19:40 +0000 [thread overview]
Message-ID: <1ebf86cff330eb15c02249f0dac415a8aff99f49.camel@hammerspace.com> (raw)
In-Reply-To: <A862CFCD-76A2-4373-8F44-F156DB38E6A5@redhat.com>
On Sun, 2019-09-08 at 07:39 -0400, Benjamin Coddington wrote:
> On 6 Sep 2019, at 16:50, Chuck Lever wrote:
>
> > > On Sep 6, 2019, at 4:47 PM, Jason L Tibbitts III <
> > > tibbs@math.uh.edu>
> > > wrote:
> > >
> > > > > > > > "JBF" == J Bruce Fields <bfields@fieldses.org> writes:
> > >
> > > JBF> Those readdir changes were client-side, right? Based on
> > > that
> > > I'd
> > > JBF> been assuming a client bug, but maybe it'd be worth getting
> > > a
> > > full
> > > JBF> packet capture of the readdir reply to make sure it's legit.
> > >
> > > I have been working with bcodding on IRC for the past couple of
> > > days
> > > on
> > > this. Fortunately I was able to come up with way to fill up a
> > > directory
> > > in such a way that it will fail with certainty and as a bonus
> > > doesn't
> > > include any user data so I can feel OK about sharing packet
> > > captures.
> > > I
> > > have a capture alongside a kernel trace of the problematic
> > > operation
> > > in
> > > https://www.math.uh.edu/~tibbs/nfs/. Not that I can
> > > particularly
> > > tell
> > > anything useful from that, but bcodding says that it seems to
> > > point
> > > to
> > > some issue in sunrpc.
> > >
> > > And because I can easily reproduce this and I was able to do a
> > > bisect:
> > >
> > > 2c94b8eca1a26cd46010d6e73a23da5f2e93a19d is the first bad commit
> > > commit 2c94b8eca1a26cd46010d6e73a23da5f2e93a19d
> > > Author: Chuck Lever <chuck.lever@oracle.com>
> > > Date: Mon Feb 11 11:25:41 2019 -0500
> > >
> > > SUNRPC: Use au_rslack when computing reply buffer size
> > >
> > > au_rslack is significantly smaller than (au_cslack << 2).
> > > Using
> > > that value results in smaller receive buffers. In some cases
> > > this
> > > eliminates an extra segment in Reply chunks (RPC/RDMA).
> > >
> > > Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> > > Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
> > >
> > > :040000 040000 d4d1ce2fbe0035c5bd9df976b8c448df85dcb505
> > > 7011a792dfe72ff9cd70d66e45d353f3d7817e3e M net
> > >
> > > But of course, I can't say whether this is the actual bad commit
> > > or
> > > whether it just introduced a behavior change which alters the
> > > conditions
> > > under which the problem appears.
> >
> > The first place I'd start looking is the XDR constants at the head
> > of
> > fs/nfs/nfs4xdr.c
> > having to do with READDIR.
> >
> > The report of behavior changes with the use of krb5p also makes
> > this
> > commit plausible.
>
> After sprinkling the printk's, we're coming up one word short in the
> receive
> buffer. I think we're not accounting for the xdr pad of buf->pages
> for
> NFS4
> readdir -- but I need to check the RFCs. Anyone know if v4 READDIR
> results
> have to be aligned?
>
> Also need to check just why krb5i is the only auth that cares..
>
I'm not seeing that. If you look at commit 02ef04e432ba, you'll see
that Chuck did add a 'padding term' to decode_readdir_maxsz in the
NFSv4 case.
The other thing to remember is that a readdir 'dirlist4' entry is
always word aligned (irrespective of the length of the filename), so
there is no padding that needs to be taken into account.
I think we probably rather want to look at how auth->au_ralign is being
calculated for the case of krb5i. I'm really not understanding why
auth->au_ralign should not take into account the presence of the mic.
Chuck?
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com
next prev parent reply other threads:[~2019-09-08 15:19 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <ufak1bhyuew.fsf@epithumia.math.uh.edu>
2019-08-22 19:39 ` Regression in 5.1.20: Reading long directory fails Jason L Tibbitts III
2019-08-28 17:46 ` J. Bruce Fields
2019-08-28 18:29 ` Jason L Tibbitts III
2019-08-28 18:33 ` J. Bruce Fields
2019-09-03 15:49 ` Jason L Tibbitts III
2019-09-03 18:02 ` Wolfgang Walter
2019-09-03 19:06 ` Jason L Tibbitts III
2019-09-03 19:08 ` Chuck Lever
2019-09-03 21:37 ` Wolfgang Walter
2019-09-04 1:50 ` Jason L Tibbitts III
2019-09-06 14:48 ` J. Bruce Fields
2019-09-06 20:47 ` Jason L Tibbitts III
2019-09-06 20:50 ` Chuck Lever
2019-09-08 11:39 ` Benjamin Coddington
2019-09-08 15:19 ` Trond Myklebust [this message]
2019-09-08 15:48 ` Chuck Lever
2019-09-08 16:47 ` Trond Myklebust
2019-09-08 16:51 ` Chuck Lever
2019-09-11 16:25 ` Benjamin Coddington
2019-09-11 16:39 ` Chuck Lever
2019-09-11 17:26 ` Benjamin Coddington
2019-09-11 17:27 ` Benjamin Coddington
2019-09-11 17:29 ` Chuck Lever
2019-09-11 17:40 ` Benjamin Coddington
2019-09-11 17:43 ` Chuck Lever
2019-09-11 17:59 ` Benjamin Coddington
2019-09-11 17:50 ` Benjamin Coddington
2019-09-11 17:54 ` Chuck Lever
2019-09-12 12:29 ` Benjamin Coddington
2019-09-12 12:53 ` Trond Myklebust
2019-09-12 13:08 ` Benjamin Coddington
2019-09-12 13:13 ` J. Bruce Fields
2019-09-12 13:25 ` Trond Myklebust
2019-09-12 13:35 ` Benjamin Coddington
2019-09-12 13:14 ` Trond Myklebust
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